modern setup

Streamline CI template

use setup.cfg instead of setup.py

Best practices

SImplify/uniformize command line to just findssh, thereby also templatizing self-test

README: rst=>md

Code quality: flake8, mypy typing

Enforce better code quality, requiring Python >= 3.6 with

• flake8
• mypy (enforces type hints)

Multi-threaded 100x speedup

Uses 100 threads by default for 100x speedup. Tested on Windows and Linux to have this speedup (didn't bother to test Mac).

Python module or command-line use

allowed "import findssh" as well as the traditional command-line use.